Audio devices are extremely popular and are widely used. Examples of audio devices include CD players, MP-3 players, car audio systems, etc, and can also be considered to include visual devices that output audio, for example, DVD players, MPEG players, mobile phones, pagers, personal digital assistants, electronic organizers, etc. Most of these audio devices are now equipped with noise cancellation systems that cancel environmental noise from the received signals to allow a user to enjoy perfect sound quality.
However, naturally, hearing sense is very important to a person in order for them to navigate safely around their surrounding environment. When a user is listening to audio, for example via headphones, environmental noise is often cancelled. By cancelling environmental noise, important (and often life-vital) sounds are also cancelled, leaving the user to rely mostly on his visual senses whilst the audio that they are listening to via the headphones does not correspond to the situation around the user. This can lead to dangerous situations that could risk the life of a user. For example, in a situation where a user is crossing a road on a green light and there is an ambulance approaching at high speed, the user would not hear the siren of the ambulance and would be unaware of the danger.
There is therefore a need for a system that provides a user with superior quality sound while not compromising the user's safety.
A number of solutions have been proposed based on the recognition of a sudden change of environmental sound level (dB). These systems react on any sudden change in environmental sounds by stopping the audio playback so that environmental sounds can be heard. However, this is not practical when an audio device is used in a busy city as the system would be constantly triggered by the very dense audio environment.
Another solution not only reacts on the basis of sound level, but also recognizes the type of sound (for example, a car horn) and stops the audio play back based on that information.
However, by simply stopping the audio playback, a user only really knows that something has just happened (or is happening) and is not aware of what has happened and where relative to them. This is problematic when the user is in a dangerous situation as it prevents the user from acting quickly to avoid a potential danger. Also, if the audio playback was stopped due to another person calling the user's name, a user would still only be aware that something has happened and would not realise that that his name had been called. It is therefore not enough to only know that something has just happened (or is happening), but it is also important to know what happened and where relative to the user.
US 2007/0223717 discloses a headset for reproducing audio that also preserves the spatial characteristics of the ambient sound (e.g. the direction from which the ambient sound originates). This headset includes an input that receives an audio signal from electronic equipment and at least one microphone that receives ambient sound, which is converted to an ambient sound signal. The audio signal and the ambient sound signal are combined and the combined signal is provided to at least one earpiece of the headset such that the headset reproduces the ambient sound in combination with audio from the audio signal. A user of the headphones is able to adjust the ratio by which the audio signal and the ambient sound signal are combined and is able to adjust the volume of the combined signals.
However, by combining the ambient sound signal with the audio signal, the quality of the audio signal is continually affected, which would spoil the enjoyment for the user listening to the audio. To improve the quality of the audio signal, the user could choose to block most or all of the environmental sounds. However, this solution would then fail to alert the user of a potentially interesting or potentially dangerous situation.
There is therefore a need for a system that can increase the awareness of a user of an audio device to certain environmental sounds whilst maintaining the quality of the audio.